assigning partition letters in dual boot
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From: Tom Orle on 31 Dec 2009 13:56 Happy New year all, I'm having an interesting challenge to keep me busy over this long weekend. The basic question is: what, on a dual boot W7 system, determines how partition letters get reassigned? I installed W7 Pro x64 on an existing Win XP Pro 32 bit system as dual boot. But first I cloned my existing drive just as a precaution. The initial partitions on both 500 GB drives were C (XP boot), D, E and a newly created F for W7. Install #1: I installed W7 into the F partition and when done I booted into W7. As expected it made the F partition the C partition, D and E remained D and E and the XP partition became G since somehow the DVD drive slipped in as F. Install # 2: Two weeks later I wanted to install W7 onto the cloned drive. I didn't do anything different than I did during Install # 1, but this time when W7 booted up F became C as expected, but the old XP partition slipped into the D slot and the old D and E were shifted to E and F!! The DVD drive became G. My question now is: why did these 2 identical installs come up with different partition letter assignments? And how can I force the assignments to look like my first attempt since I like keeping my data partitions, D & E the same under XP and W7? Not that it matters to the system as it works either way, but it's less confusing to me since I would always know that certain data is on the same partition no matter which OS I'm logged on to. It seems that he letter swaps must happen in the boot manager. However I checked into BCDEDIT and the boot tab in msconfig, but found no way to affect the letter allocations. Any ideas and suggestions would be very welcome. Thanks ... -=tom=-
From: Kerry Brown on 31 Dec 2009 15:11 It's very hard to determine how Windows will enumerate the drives and partitions in advance. Fortunately you can easily change the drive letters after the fact. Run diskmgmt.msc then right click a partition or drive to change the drive letter. Do not change the letter for the partition that the currently running version of Windows is installed on. You should also not change the letter for partitions where you have installed programs for the currently running version of Windows. If it's just data you should be OK. -- Kerry Brown MS-MVP - Windows Desktop Experience: Systems Administration http://www.vistahelp.ca/phpBB2/ "Tom Orle" <xspam.torle(a)comcast.net> wrote in message news:ppppj5d4pbpp4ejd61ofeu25rmr45t0cg4(a)4ax.com... > Happy New year all, > > I'm having an interesting challenge to keep me busy over this long > weekend. The basic question is: what, on a dual boot W7 system, > determines how partition letters get reassigned? > > I installed W7 Pro x64 on an existing Win XP Pro 32 bit system as dual > boot. But first I cloned my existing drive just as a precaution. > > The initial partitions on both 500 GB drives were C (XP boot), D, E > and a newly created F for W7. > Install #1: I installed W7 into the F partition and when done I booted > into W7. As expected it made the F partition the C partition, D and E > remained D and E and the XP partition became G since somehow the DVD > drive slipped in as F. > > Install # 2: Two weeks later I wanted to install W7 onto the cloned > drive. I didn't do anything different than I did during Install # 1, > but this time when W7 booted up F became C as expected, but the old XP > partition slipped into the D slot and the old D and E were shifted to > E and F!! The DVD drive became G. > > My question now is: why did these 2 identical installs come up with > different partition letter assignments? > And how can I force the assignments to look like my first attempt > since I like keeping my data partitions, D & E the same under XP and > W7? Not that it matters to the system as it works either way, but it's > less confusing to me since I would always know that certain data is on > the same partition no matter which OS I'm logged on to. > > It seems that he letter swaps must happen in the boot manager. However > I checked into BCDEDIT and the boot tab in msconfig, but found no way > to affect the letter allocations. > > Any ideas and suggestions would be very welcome. > Thanks ... > > -=tom=- > >
From: R. C. White on 1 Jan 2010 00:12 Hi, Tom. When we install Win7 by booting from the Win7 DVD, Setup has no idea what letters have already been assigned, so it follows its own rules for the initial assignment. First, it assigns the letter C: to whichever partition we choose to "install" it in. This becomes the Win7 "boot volume". Then it assigns other letters, starting with D:, usually assigned to the "system volume", if that is not the same partition as the boot volume. (This rule changed with Vista; WinXP and prior assigned C: to the system volume, then the next available letter to its own boot volume, if different.) After installation, we can use Disk Management to change letters on all volumes except the boot volume and, if different, the system volume. The Status column of Disk Management shows us which partition has the Boot status and the System status; the two "status" labels may or may not be on the same partition. (For these "backwards" definitions, see KB 314470, Definitions for system volume and boot volume http://support.microsoft.com/kb/314470/EN-US/ ) But when we boot into an existing Windows installation, then run Win7 Setup from that desktop, Setup can see the drive letters already assigned by that existing OS and it will use the same letters, even for the boot and system volumes. So, when we add Win7 to an existing Windows system to create a multi-boot system, we can either have it "inherit" the existing letters (by running Setup from the existing desktop) or have it assign "C:" to whichever partition we install it into (by booting from the DVD). Note that Windows (any version) is just as happy running from X:\Windows as from C:\Windows. Most users develop a "drive C: mindset" early in their computing experience and have trouble adapting to having Windows on any other partition - but Windows itself has no such hangup. If you want your drive letters to be consistent as you reboot between different Windows installations, then boot into the first system, assign the letters you want, and then run Setup from there to install the second system - and the 3rd and 4th OSes, if you want to use that many. Only ONE can say it's on Drive C:, but neither Vista nor the others will care if Vista is on Drive V:. And nobody cares if we skip letters and choose some that are easy to remember; I like to leave gaps that I can fill in later if I get a new thumb drive or other device. Win7 has added a new wrinkle by creating a small (100 MB) partition to use as the System Volume, but that happens only when Win7 is installed on a computer without an existing OS. I've read about this, but haven't run into it yet, since I was already multi-booting before installing Win7, so it simply updated the startup files on my existing System Partition. BCDEdit uses drive letters, but it cannot change them. We use Setup to assign letters initially and Disk Management to reassign them - except for the system and boot volumes. RC -- R. C. White, CPA San Marcos, TX rc(a)grandecom.net Microsoft Windows MVP Windows Live Mail 2009 (14.0.8089.0726) in Win7 Ultimate x64 "Tom Orle" <xspam.torle(a)comcast.net> wrote in message news:ppppj5d4pbpp4ejd61ofeu25rmr45t0cg4(a)4ax.com... > Happy New year all, > > I'm having an interesting challenge to keep me busy over this long > weekend. The basic question is: what, on a dual boot W7 system, > determines how partition letters get reassigned? > > I installed W7 Pro x64 on an existing Win XP Pro 32 bit system as dual > boot. But first I cloned my existing drive just as a precaution. > > The initial partitions on both 500 GB drives were C (XP boot), D, E > and a newly created F for W7. > Install #1: I installed W7 into the F partition and when done I booted > into W7. As expected it made the F partition the C partition, D and E > remained D and E and the XP partition became G since somehow the DVD > drive slipped in as F. > > Install # 2: Two weeks later I wanted to install W7 onto the cloned > drive. I didn't do anything different than I did during Install # 1, > but this time when W7 booted up F became C as expected, but the old XP > partition slipped into the D slot and the old D and E were shifted to > E and F!! The DVD drive became G. > > My question now is: why did these 2 identical installs come up with > different partition letter assignments? > And how can I force the assignments to look like my first attempt > since I like keeping my data partitions, D & E the same under XP and > W7? Not that it matters to the system as it works either way, but it's > less confusing to me since I would always know that certain data is on > the same partition no matter which OS I'm logged on to. > > It seems that he letter swaps must happen in the boot manager. However > I checked into BCDEDIT and the boot tab in msconfig, but found no way > to affect the letter allocations. > > Any ideas and suggestions would be very welcome. > Thanks ... > > -=tom=-
From: R. C. White on 1 Jan 2010 00:12 Hi, Tom. "Drive" letters are like shifting sands. Especially when dual-booting. Please don't rely on them. Windows pays very little attention to them. When dual-booting, OS #1 cannot read OS #2's Registry, so it has no idea what letters OS #2 might have assigned. So what is Drive X: in WinXP might be Drive H: in Win7 - or vice versa. To make the drive letters consistent between the two OSes, you need to run Disk Management in each OS and assign the same letters in each of them. But there is a BIG fly in this ointment: Letters for the System Volume and Boot Volume are assigned by Setup when each OS is installed and cannot be changed (by us mere mortals) after installation - except by running Setup again, which means re-installing. The terms "system volume" and "boot volume" are VERY important in understanding drive letter assignments - and the definitions are backward from most users' expectations. As often said, we BOOT from the SYSTEM partition and keep the operating SYSTEM files in the BOOT volume. Carefully read KB 314470, Definitions for system volume and boot volume http://support.microsoft.com/kb/314470/EN-US/ . Until you get these definitions firmly in mind, dual-booting is not going to make any sense. WinXP Setup assigns the letter C: to the System Partition, then assigns other letters according to its built-in algorithm. In the typical system, with the first partition on the first HDD holding both the System and Boot volumes, this means that the whole shebang is in Drive C:. Most users never get past this basic arrangement and never need to really understand drive letters. Vista Setup assigns the letter C: to its own Boot Volume - wherever that may be - even if it is the 3rd partition on the second HDD. Whichever partition you choose to install Vista in will become Drive C:. That means that, unless you install it into the System Partition, the System Partition will have to be assigned a different letter: Drive D:. "Tom Orle" <xspam.torle(a)comcast.net> wrote in message news:ppppj5d4pbpp4ejd61ofeu25rmr45t0cg4(a)4ax.com... > Happy New year all, > > I'm having an interesting challenge to keep me busy over this long > weekend. The basic question is: what, on a dual boot W7 system, > determines how partition letters get reassigned? > > I installed W7 Pro x64 on an existing Win XP Pro 32 bit system as dual > boot. But first I cloned my existing drive just as a precaution. > > The initial partitions on both 500 GB drives were C (XP boot), D, E > and a newly created F for W7. > Install #1: I installed W7 into the F partition and when done I booted > into W7. As expected it made the F partition the C partition, D and E > remained D and E and the XP partition became G since somehow the DVD > drive slipped in as F. > > Install # 2: Two weeks later I wanted to install W7 onto the cloned > drive. I didn't do anything different than I did during Install # 1, > but this time when W7 booted up F became C as expected, but the old XP > partition slipped into the D slot and the old D and E were shifted to > E and F!! The DVD drive became G. > > My question now is: why did these 2 identical installs come up with > different partition letter assignments? > And how can I force the assignments to look like my first attempt > since I like keeping my data partitions, D & E the same under XP and > W7? Not that it matters to the system as it works either way, but it's > less confusing to me since I would always know that certain data is on > the same partition no matter which OS I'm logged on to. > > It seems that he letter swaps must happen in the boot manager. However > I checked into BCDEDIT and the boot tab in msconfig, but found no way > to affect the letter allocations. > > Any ideas and suggestions would be very welcome. > Thanks ... > > -=tom=- > >
From: R. C. White on 1 Jan 2010 00:25
Oops! Sorry for the double post. This second one was an earlier draft that I meant to delete, not to send. Please ignore it. :>( RC -- R. C. White, CPA San Marcos, TX rc(a)grandecom.net Microsoft Windows MVP Windows Live Mail 2009 (14.0.8089.0726) in Win7 Ultimate x64 "R. C. White" <rc(a)grandecom.net> wrote in message news:uE$9SEqiKHA.5604(a)TK2MSFTNGP04.phx.gbl... > Hi, Tom. > > "Drive" letters are like shifting sands. Especially when dual-booting. > Please don't rely on them. Windows pays very little attention to them. > <SNIP> |